Heat pump system

ABSTRACT

Provided is a heat pump system ( 10, 10 A) for a conditioned space comprising a first thermal fluid circuit adapted to selectably operate to circulate a thermal fluid therein, and a second thermal fluid circuit adapted to selectably operate to circulate the thermal fluid therein. The first thermal fluid circuit may comprise a compressor ( 15 ), a first heat exchanger ( 11 ), and a passage ( 55 ) of a heat accumulator ( 50 ). The second thermal fluid circuit may bypass the first heat exchanger ( 11 ), or the passage ( 55 ) of the heat accumulator ( 50 ), or both. The second thermal fluid circuit may comprise the compressor ( 15 ), and a second heat exchanger ( 12 ).

TECHNICAL FIELD

The present invention generally relates to a heat pump system. Moreparticularly, the present invention relates to a heat pump systememploying a heat accumulator to defrost a heat exchanger in the system.Most particularly, the present invention relates to a heat pump system,where the accumulator obtains waste heat from the compressor in thesystem.

BACKGROUND

A heat pump is a device that transfers thermal energy from a heat sourceto a heat sink. Heat pumps can move thermal energy in a directionopposite to the direction of the spontaneous heat flow. A heat pump usesenergy to accomplish the desired transfer of thermal energy from heatsource to heat sink.

Compressor driven air conditioners are one example of a heat pump;however, the term heat pump is more general and applies to devices whichare adapted for use for space heating, or space cooling. When a heatpump is used for heating, it may use the same basic refrigeration cycleemployed by an air conditioner or a refrigerator, with the differencethat it outputs heat into the conditioned space rather than into thesurrounding environment. In this use, heat pumps generally absorb heatfrom a heat source region, such as, without limitation, cooler externalair or from the ground. Heat pumps are sometimes used to provide heatingbecause less high grade (low entropy) energy is required for theiroperation than appears in the output heat. That is, in a heat pump, muchor most of the energy for heating may be absorbed from a heat sourceregion and only a small fraction of the energy for heating needs to comefrom electricity or some other high grade energy source. Because theheat output to the heat sink may comprise both the heat absorbed fromthe heat source, and the high grade heat consumed to transfer of thermalenergy from heat source region to heat sink region, the heat output maybe several times larger than the high grade energy consumed. As aconsequence, the system coefficient of performance (COP) of a heat pumpmay be substantially greater than 1. The system coefficient ofperformance (COP) of some heat pumps may be 3 or 4.

One issue in operation of known heat pumps is that the heat exchangerabsorbing heat from a heat source region may frost when operating in lowtemperature environments. To defrost the frosted heat exchanger, someheat pumps may stop heating the heat sink region and switch to absorbingheat from the previous heat sink region to provide heat to defrost thefrosted heat exchanger. Where the previous heat sink region is aconditioned space that is desirable to heat or keep warm, this removalof heat to defrost the frosted heat exchanger is undesirable and mayresult in an uncomfortable or undesired decrease in temperature.

SUMMARY OF THE INVENTION

Provided is a heat pump system for a conditioned space comprising afirst thermal fluid circuit adapted to selectably operate to circulate athermal fluid therein, and a second thermal fluid circuit adapted toselectably operate to circulate the thermal fluid therein. The firstthermal fluid circuit may comprise a compressor, a first heat exchanger,and a passage of a heat accumulator. The second thermal fluid circuitmay bypass the passage of the heat accumulator. The second thermal fluidcircuit may comprise the compressor, and a second heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a heat pump system in accordance withthe present invention depicted in a cooling mode of operation.

FIG. 2 is a schematic diagram similar to FIG. 1 depicted in a heatingmode of operation.

FIG. 3 is a schematic diagram similar to FIG. 1 depicted in a defrostingmode of operation.

FIG. 1A is a schematic diagram mostly similar to FIG. 1 differing in theembodiment of the heat accumulator shown and depicted in a cooling modeof operation.

FIG. 2A is a schematic diagram mostly similar to FIG. 1 differing in theembodiment of the heat accumulator shown and depicted in a heating modeof operation.

FIG. 3A is a schematic diagram mostly similar to FIG. 1 differing in theembodiment of the heat accumulator shown and depicted in a defrostingmode of operation.

The following description and the annexed drawings set forth in detailcertain illustrative aspects of the claimed subject matter. Theseaspects are indicative, however, of but a few of the various ways inwhich the principles of the innovation may be employed and the claimedsubject matter is intended to include all such aspects and theirequivalents. Other advantages and novel features of the claimed subjectmatter will become apparent from the following detailed description ofthe innovation when considered in conjunction with the drawings.

DETAILED DESCRIPTION

A heat pump system according to the concepts of the present subjectmatter is generally indicated by the numbers 10, 10A in the drawings.Heat pump system 10, 10A includes a first heat exchanger 11, which is incommunication with a conditioned space. As the term is used herein,unless otherwise noted, a “conditioned space” may be any region that isheated or cooled by the operation of the heat pump system 10, 10A. Aconditioned space refers to the region to which or from which the heatpump system 10, 10A is adapted to pump heat. Without limitation, in someembodiments the conditioned space may be a room, building, vehicleinterior, refrigerator interior, freezer interior, or other appliance,device, or structure that comprises a space to be temperaturecontrolled. In some non-limiting embodiments, the first heat exchanger11 may be referred to as an indoor heat exchanger or a conditioned spaceheat exchanger. Heat pump system 10, 10A also includes a second heatexchanger 12, which is in communication with an environment, which,without limitation, may be atmospheric air, or a geothermal region, aroom, or some other region differing from the conditioned space, andmay, in some non-limiting embodiments, be referred to as an outdoor heatexchanger or an environmental heat exchanger. When the conditioned spaceis to be cooled, the heat pump system 10, 10A operates to pump heat fromthe conditioned space to the environment. When the conditioned space isto be heated, the heat pump system 10, 10A operates to pump heat to theconditioned space from the environment. Heat pump system 10, 10A furtherincludes a compressor 15. The heat pump system 10, 10A also includes afirst expansion valve 21, a second expansion valve 22, a third expansionvalve 23, and a four-way valve 24. The heat pump system 10, 10A alsoincludes a thermal fluid, which may be any suitable liquid or gas usedto transfer heat through the system. The thermal fluid may comprise arefrigerant chosen by one or ordinary skill in the art. Withoutlimitation, a refrigerant may comprise a chlorofluorocarbon, achlorofluoroolefin, a hydrochlorofluorocarbon, ahydrochlorofluoroolefin, a hydrofluorocarbon, a hydrofluoroolefin, ahydrochlorocarbon, a hydrochloroolefin, a hydrocarbon, a hydroolefin, aperfluorocarbon, a perfluoroolefin, a perchlorocarbon, aperchloroolefin, a halon, or combinations thereof. Without limitation, arefrigerant may comprise, R717, also known as ammonia, and having theformula NH₃; R744, also known as carbon dioxide, and having the formulaCO₂; R12, also known as dichlorodifluoromethane, and having the formulaCCl₂F₂; DME, also known as dimethyl ether, and having the formulaCH₃OCH₃; R-124, also known as 1-Chloro-1,2,2,2-tetrafluoroethane, andhaving the formula C₂HClF₄; Freon 142b, also known as1-Chloro-1,1-difluoroethane, and having the formula CH₃CClF₂; R-134a,also known as 1,1,1,2-Tetrafluoroethane, and having the formula CH₂FCF₃;HFO-1234yf, also known as 2,3,3,3-Tetrafluoropropene, and having theformula CH₂═CFCF₃; R-22 also known as chlorodifluoromethane, and havingthe formula CHClF₂; R-410A, a mixture of difluoromethane, CH₂F₂, andpentafluoroethane, CHF₂CF₃; propane, having the formula C₃H₈; orcombinations thereof. There are many other acceptable refrigerants whichmay be used. The present subject matter is not limited by refrigeranttype.

Thermal fluid may comprise a liquid that changes phases as it undergoescompression or expansion in the system including, but not limited to,refrigerants such as R-134a and the like.

Compressor 15 includes a compressor discharge 16 and a compressorsuction 17. The compressor discharge 16 is in communication with thefour-way valve 24. The four-way valve 24, when in cooling mode (shown inFIGS. 1 and 1A), provides communication between the compressor discharge16 and second heat exchanger 12 allowing compressed and heated thermalfluid, generally indicated by the arrows, to enter second heat exchanger12 at a first port 31. The thermal fluid flows through second heatexchanger 12 and exits at a second port outlet 32 that is incommunication with second expansion valve 22 and third expansion valve23. In the cooling mode shown in FIGS. 1 and 1A, second expansion valve22 is closed causing the thermal fluid exiting the second heat exchanger12 to flow through third expansion valve 23. Third expansion valve 23 isin fluid communication with first expansion valve 21 and first heatexchanger 11. In the cooling mode shown in FIGS. 1 and 1A, the firstexpansion valve 21 is closed causing the thermal fluid exiting thirdexpansion valve 23 to flow into first heat exchanger 11 at first port33. That is, in the cooling mode shown in FIGS. 1 and 1A, the firstexpansion valve 21 is closed, the second expansion valve 22 is closed,and the third expansion valve 23 is open.

As the thermal fluid flows through the second heat exchanger 12, heat isreleased to the environment such that the thermal fluid exiting secondheat exchanger 12 has less thermal energy; that is, is cooler. Thecooled thermal fluid exiting the second heat exchanger 12 is furthercooled as it flows through third expansion valve 23 and enters firstheat exchanger 11. First heat exchanger 11 is, thus, used to cool theconditioned space S such as, without limitation, by cooling air providedto the conditioned space S. To facilitate this operation, in somenon-limiting embodiments, a first fan 41 may be provided to direct airover the first heat exchanger 11 and into the conditioned space S.Ducting or vents may be provided to route air passing over first heatexchanger 11 to the conditioned space S in a devised manner. A secondfan 42, likewise, may be provided to direct air over the second heatexchanger 12 to facilitate heat transfer from the second heat exchanger12 to the environment. The thermal fluid exits first heat exchanger 11at a second port 34. The second port 34 is in fluid communication withsecond valve 22 and four-way valve 24. As previously mentioned, incooling mode, second valve 22 is closed such that the thermal fluidexiting first heat exchanger 11 is directed by four-way valve 24 to thecompressor suction 17.

With reference to FIGS. 2 and 2A, a heating mode for each of the heatpump systems 10 and 10A is shown. In the heating mode, four-way valve 24is oriented such that thermal fluid exiting compressor 15 via compressordischarge 16 is directed toward first heat exchanger 11. As in thecooling mode, the first and second expansion valves 21, 22 are closed.Heated thermal fluid exiting the compressor 15 flows through first heatexchanger 11 to provide heat to the conditioned space. After providingheat to the conditioned space, the thermal fluid exits the first heatexchanger 11 and is directed through third expansion valve 23 furthercooling the thermal fluid before it is directed to second heat exchanger12. The cooled thermal fluid entering the second heat exchanger 12 iswarmed by heat from the environment and exits second heat exchanger 12to flow through four-way valve 24 to the compressor suction 17.

In some embodiments, a heat pump system 10, 10A may comprise a heataccumulator 50, 150 in thermal communication with the compressor 15. Afirst non-limiting embodiment of a heat accumulator 50 is shown in FIGS.1, 2, and 3 and a second non-limiting embodiment of a heat accumulator150 is shown in FIGS. 1A, 2A, and 3A. The thermal communication betweenthe heat accumulators 50, 150 and the compressor 15 is an adaptationthat allows heat from operation of the compressor 15 which wouldotherwise be dismissed to the atmosphere and wasted, that is, wasteheat, to be removed from the compressor 15 and stored in the heataccumulator 50, 150.

In the non-limiting embodiment shown in FIGS. 1-3, heat accumulator 50wraps around the housing 51 of compressor 15, may comprise a solidsurface in direct thermal contact with the compressor housing 51, andmay be adapted to absorb waste heat from the compressor primarily byconduction. Herein unless otherwise noted, transfer of heat primarily bya particular means indicates that the particular means is the primaryheat transfer means, such that more heat is transferred by theparticular means than by either of the other recognized heat transfermeans. For example and without limitation, transfer of heat primarily byconduction indicates that conduction is the primary heat transfer means,such that more heat is transferred by conduction than by either of theother heat transfer means, convection or radiation. In the non-limitingembodiment shown in FIG. 3, heat accumulator 50 has a surface 52 thatcontacts compressor housing 51. Surface 52 may conform to the housing 51to maximize the contact with compressor 15. As shown in FIG. 3, when acylindrical compressor housing 51 is used, surface 52 may be concave toencompass a greater portion of compressor housing 51. As shown, surface52 may define an arc matching an arc defined by the circular shape ofhousing 51. The accumulator body 53 may follow the arc of surface 52, asshown. As shown in FIG. 3, body 53 of accumulator 50 include asemi-circular portion 54 that conforms to at least part of the outersurface of compressor 15 and an end portion 56 that extends at a tangentto compressor housing 51. The accumulator may include a body 53 whichmay be formed of a heat absorption material including but not limited toplastics, ceramics, oxidized metals, black chrome, or other materialswith high absorption and/or low emissivity properties. In otherembodiments, a heat accumulator may comprise a fluid mass, such as,without limitation, air, water, or oil, adapted to absorb waste heatfrom the compressor primarily by forced or natural convection. In otherembodiments, a heat accumulator may be adapted to absorb waste heat fromthe compressor primarily by radiation.

As shown in FIG. 3, a passage 55 may be provided at least partiallywithin the body 53 to route a thermal fluid through body 53 of heataccumulator 50 to transfer heat accumulated within body 53 to thethermal fluid. Passage 55 may be integrally formed within body 53 and inthis sense may simply be a passage within the body 53 or passage 55 maybe a separate conduit or other structure placed in thermal contact withbody 53 through which thermal fluid is routed. In the non-limitingexample depicted in FIG. 3, passage 55 is a conduit, which may bemanufactured from a heat conductive material including, but not limitedto, metals such as, for example, copper or aluminum. Passage 55 islocated within the body 53 of heat accumulator 50. The passage 55 hastwo openings that each act as an inlet or outlet depending on the flowof thermal fluid through the passage 55. Passage 55 may extendthroughout accumulator body 53 and may take a straight route throughbody 53 or include a non-straight path to increase the surface area ofpassage 55 within accumulator 50. For example, to form a non-straightpath, passage 55 may include a number of turns that route the thermalfluid back and forth across the length and/or width of the heataccumulator body 53 such that passage 55 is a coil or otherwiseconvoluted. In the non-limiting embodiment shown in FIGS. 1-3, passage55 is in thermal communication with the heat accumulator 50, is in fluidcommunication with the compressor 15, and is in selectable fluidcommunication with first heat exchanger 11 through valve 21.

As shown, passage 55 may be located within only a portion of heataccumulator 50. For example, passage 55 may be located generally in theportion of accumulator 50 in closest contact with compressor 15. In theexample shown, passage 55 generally resides in the concave portion 54 ofaccumulator 50 with an inlet 57 located near one end of thesemi-circular portion 54 and an exit 58 at the opposite end ofsemi-circular portion 54. In this example, passage 55 traces a somewhatsemi-circular path and generally conforms to the shape of surface 52. Inother embodiments, passage 55 may be located fully within heataccumulator 50.

In the non-limiting embodiment shown in FIGS. 1A-3A, heat accumulator150 is in thermal communication with compressor 15 by a heat transferconduit 171. Heat transfer conduit 171 may wrap around the housing 51 ofcompressor 15, may comprise a solid surface in direct thermal contactwith the compressor housing 51, and may be adapted to absorb waste heatfrom the compressor primarily by conduction. Heat transfer conduit 171may conform to the housing 51 to increase the contact with compressor15. In other embodiments, the thermal engagement between heat transferconduit 171 and the compressor 15 may entail indirect engagement withthe compressor 15 or engagement with internal regions or components ofthe compressor 15. In the non-limiting embodiment shown in FIGS. 1A-3A,heat accumulator 150 defines a volume containing a thermal storagematerial 152. The accumulator 150 may include a body 153 formed of aheat absorption material including but not limited to plastics,ceramics, oxidized metals, black chrome, or other materials with highabsorption and/or low emissivity properties. As noted above, in otherembodiments, a heat accumulator 150 may comprise a fluid mass, such as,without limitation, air, water, or oil, adapted to absorb waste heatfrom the compressor primarily by forced or natural convection. In otherembodiments, a heat accumulator 150 may be adapted to absorb waste heatfrom the compressor primarily by radiation.

As shown in FIGS. 1A-3A, a passage 155 may be provided at leastpartially within the body 153 to route a thermal fluid through body 153of heat accumulator 150 to transfer heat accumulated from heat transferconduit 171 to heat accumulator 150. Passage 155 may be integrallyformed within body 153 and in this sense may simply be a passage withinthe body 153 or passage 155 may be a separate conduit or other structureplaced in thermal contact with body 153 through which thermal fluid isrouted. In the non-limiting example depicted in FIGS. 1A-3A, passage 155is a conduit, which may be manufactured from a conductive materialincluding, but not limited to, metals such as, without limitation,copper or aluminum. Passage 155 is located within the body 153 of heataccumulator 150.

The passage 155 forms part of a heat transfer loop between compressor 15and the heat accumulator 150. The flow of thermal fluid through thepassage 155 may be driven by a pump 173. Passage 155 may extendthroughout body 153 and may take a straight route through body 153 orinclude a non-straight path to increase the surface area of passage 155within accumulator 150. For example, to form a non-straight path,passage 155 may include a number of turns that route the thermal fluidback and forth across the length and/or width of the heat accumulatorbody 153 such that passage 155 is a coil or otherwise convoluted.

With reference to the embodiment shown FIG. 1A-3A, heat accumulator 150may contain a thermal reservoir material 152 suitable for storing heat.Exemplary thermal reservoir materials 152 include, but are not limitedto, water, and a mixture of water and antifreeze or another additive. Inthe non-limiting embodiment shown in FIGS. 1A-3A, passage 159 is atleast partially positioned with body 153 and provides a path to route athermal fluid through the thermal reservoir material 152 of heataccumulator 150 to transfer heat accumulated therein to the thermalfluid. In the non-limiting embodiment shown in FIGS. 1A-3A, passage 159is in thermal communication with the heat accumulator 150, is in fluidcommunication with the compressor 15, and is in selectable fluidcommunication with first heat exchanger 11 through valve 21.

With continued reference to the non-limiting embodiment shown FIG. 3A,operation of the heat pump assembly 10A in a defrosting mode is shown.The heat pump assembly 10A may include two valves, such as, withoutlimitation, valve 21 and valve 22, to separate the thermal fluid flowinto two conjoined circuits during defrosting. In the non-limitingembodiment shown in FIG. 3A, the thermal fluid flow in the first circuitis conjoined with the thermal fluid flow in the second circuit. Acontinuous system is one in which all fluid paths, branches, or loopsare conjoined in fluid communication with one another. As used herein“simultaneous” fluid flow refers to fluid flow that occurs at the sametime or with a very slight deviation from occurring at exactly the sametime. Very slight deviation from occurring at exactly the same, on theorder of split second deviations, are acceptable and will be treated assimultaneous herein. In the non-limiting embodiment shown in FIG. 3A,the thermal fluid flow in the first circuit may be conjoined with, andcontinuous with, the thermal fluid flow in the second circuit. In thenon-limiting embodiment shown in FIG. 3A, the thermal fluid flow in thefirst circuit may be conjoined with, and simultaneous with, the thermalfluid flow in the second circuit. In the non-limiting embodiment shownin FIG. 3A, the thermal fluid flow in the first circuit may be conjoinedwith, and continuous with, and simultaneous with, the thermal fluid flowin the second circuit. In the non-limiting embodiment shown in FIG. 3A,the two valves are first expansion valve 21 and second expansion valve22. In other embodiments, other valves may be used in place of theexpansion valves 21 and 22 including but not limited to other expansiondevices, or capillary devices. In this defrosting mode of operation, thefirst expansion valve 21 and second expansion valve 22 are opened andthe four-way valve 24 oriented such that compressed, heated thermalfluid exits from the compressor discharge 16 passes through four-wayvalve 24 toward first heat exchanger 11. With second expansion valve 22open, a portion of the heated thermal fluid is directed into the secondcircuit, through second expansion valve 22 toward second heat exchanger12. In the defrost mode, third expansion valve 23 is closed to dividethe conduit into two circuits, one circuit for each heat exchanger. Theheated fluid flowing through second expansion valve 22 enters secondheat exchanger 12 to perform a defrosting operation and exits the secondheated exchanger 12 in a cooled state. Meanwhile, a portion of theheated thermal fluid from compressor discharge 16 flows into the firstcircuit to first heat exchanger 11 and is used to heat the air providedto the conditioned space. In the defrost mode, the pump 173 may be inoperation to circulate the thermal fluid in passage 155 to transfer heatfrom the compressor 15 to the heat accumulator 150. Thermal fluidexiting first heat exchanger 11 passes through first expansion valve 21and is directed to the heat accumulator 150. The thermal fluid exitingfirst expansion valve 21 is relatively cool and is heated as it passesthrough passage 159 within heat accumulator 150. The relatively warmthermal fluid exiting accumulator 150 is routed toward the outlet ofsecond heat exchanger 12 to mix with the thermal fluid exiting secondheat exchanger 12 at a junction 60. Since the thermal fluid exitingsecond heat exchanger 12 performed a defrost function, it is relativelycool and the relatively warm fluid exiting the heat accumulator 150heats the fluid exiting the second heat exchanger prior to its return tothe compressor 15. As shown, the mixed fluid from the heat accumulator150 and second heat exchanger 12 is routed through four-way valve 24 tothe compressor suction 17. In the non-limiting embodiment shown in FIG.3A, the flow in the second circuit bypasses, that is flows around ratherthan through, the first heat exchanger 11. In the non-limitingembodiment shown in FIG. 3A, the flow in the second circuit bypasses theheat accumulator 150.

With reference to the embodiment shown FIG. 1A, in the cooling mode, thepump 173 may be shut off such that the thermal fluid in passage 155 doesnot circulate to transfer heat from the compressor 15 to the heataccumulator 150. With reference to the embodiment shown FIG. 2A, in theheating mode, the pump 173 may be in operation to circulate the thermalfluid in passage 155 to transfer heat from the compressor 15 to the heataccumulator 150.

With reference to the non-limiting embodiment shown FIG. 3, operation ofthe heat pump assembly 10 in a defrosting mode is shown. The heat pumpassembly 10 may include two valves, such as, without limitation, valve21 and valve 22, to separate the thermal fluid flow into two conjoinedcircuits during defrosting. In the non-limiting embodiment shown in FIG.3, the thermal fluid flow in the first circuit may be conjoined with,and continuous with, the thermal fluid flow in the second circuit. Inthe non-limiting embodiment shown in FIG. 3, the thermal fluid flow inthe first circuit may be conjoined with, and simultaneous with, thethermal fluid flow in the second circuit. In the non-limiting embodimentshown in FIG. 3, the thermal fluid flow in the first circuit may beconjoined with, and continuous with, and simultaneous with, the thermalfluid flow in the second circuit. In the non-limiting embodiments shownin FIG. 3, the two valves are first expansion valve 21 and secondexpansion valve 22. In other embodiments, other valves may be used inplace of the expansion valves 21 and 22 including but not limited toother expansion devices, or capillary devices. In this defrosting modeof operation, the first expansion valve 21 and second expansion valve 22are opened and the four-way valve 24 oriented such that compressed,heated thermal fluid exits from the compressor discharge 16 passesthrough four-way valve 24 toward first heat exchanger 11. With secondexpansion valve 22 open, a portion of the heated thermal fluid isdirected into the second circuit, through second expansion valve 22toward second heat exchanger 12. In the defrost mode, third expansionvalve 23 is closed to divide the conduit into two circuits, one circuitfor each heat exchanger. The heated fluid flowing through secondexpansion valve 22 enters second heat exchanger 12 to perform adefrosting operation and exits the second heated exchanger 12 in acooled state. Meanwhile, a portion of the heated thermal fluid fromcompressor discharge 16 flows into the first circuit to first heatexchanger 11 and is used to heat the air provided to the conditionedspace. Thermal fluid exiting first heat exchanger 11 passes throughfirst expansion valve 21 and is directed to the heat accumulator 50. Thethermal fluid exiting first expansion valve 21 is relatively cool and isheated as it passes through the passage 55 within heat accumulator 50.The relatively warm thermal fluid exiting accumulator 50 is routedtoward the outlet of second heat exchanger 12 to mix with the thermalfluid exiting second heat exchanger 12 at a junction 60. Since thethermal fluid exiting second heat exchanger 12 has performed a defrostfunction, it is relatively cool and the relatively warm fluid exitingthe heat accumulator 50 heats the fluid exiting the second heatexchanger prior to its return to the compressor 15. As shown, the mixedfluid from the heat accumulator 50 and second heat exchanger 12 isrouted through four-way valve 24 to the compressor suction 17. In thenon-limiting embodiment shown in FIG. 3, the flow in the second circuitbypasses, that is flows around rather than through, the first heatexchanger 11. In the non-limiting embodiment shown in FIG. 3, the flowin the second circuit bypasses the heat accumulator 150.

It will be appreciated that, when using a thermal fluid that undergoes aphase change, thermal fluid exiting second heat exchanger 12 may be inthe form of a low temperature mist and thermal fluid exiting heataccumulator 50 will be an over-heated thermal fluid gas such that whenthe two flows combine the low temperature mist is heated to a gas stateavoiding any liquid pressure within the compressor suction 17.

In the example shown, the conduits, junctions, and valves are shownschematically and any suitable conduit junction, or valve may be used inaccordance with the description above. Optionally, to segregate the heataccumulator passage 55, 159 during heating and cooling operations, anaccumulator valve may be provided at the heat accumulator conduitupstream of the junction 60 where the heat accumulator outlet mergeswith the conduit extending from first port 31 of second heat exchanger12.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.

1. A heat pump system for a conditioned space comprising: a firstthermal fluid circuit adapted to selectably operate to circulate athermal fluid therein, the first thermal fluid circuit comprising acompressor, a first heat exchanger, and a passage of a heat accumulator,wherein the heat accumulator a) comprises a solid surface in contactwith the compressor, or b) is in thermal communication with thecompressor through a heat transfer conduit; and a second thermal fluidcircuit adapted to selectably operate to circulate the thermal fluidtherein, the second thermal fluid circuit bypassing the first heatexchanger and the passage of the heat accumulator, and comprising thecompressor, and a second heat exchanger.
 2. The heat pump system ofclaim 1, wherein the thermal fluid is a refrigerant.
 3. The heat pumpsystem of claim 2, wherein the passage of the heat accumulator is atleast partially within the heat accumulator.
 4. The heat pump system ofclaim 3, wherein the first thermal fluid circuit and the second thermalfluid circuit are conjoined to form a continuous system.
 5. The heatpump system of claim 3, wherein the system is adapted to be operable toflow the thermal fluid through the first thermal fluid circuit and tosimultaneously flow the thermal fluid through the second thermal fluidcircuit.
 6. The heat pump system of claim 4, wherein the system isadapted to be operable to flow the thermal fluid through the firstthermal fluid circuit and to simultaneously flow the thermal fluidthrough the second thermal fluid circuit.
 7. The heat pump system ofclaim 1, wherein the heat accumulator comprises the solid surface, thesolid surface being in direct thermal contact with the compressor. 8.The heat pump system of claim 7, wherein the heat accumulator is adaptedto transfer heat from the compressor primarily by conduction.
 9. Theheat pump system of claim 6, wherein the heat accumulator is in thermalcommunication with the compressor through the heat transfer conduit. 10.The heat pump system of claim 9, wherein the heat transfer conduitcomprises a solid surface in direct thermal contact with the compressor.11. A method of defrosting a part of a heat pump system for aconditioned space comprising: providing a heat pump system for aconditioned space comprising, a first thermal fluid circuit adapted toselectably operate to circulate a thermal fluid therein, the firstthermal fluid circuit comprising a compressor, a first heat exchanger,and a passage of a heat accumulator, wherein the heat accumulator a)comprises a solid surface in contact with the compressor, or b) is inthermal communication with the compressor through a heat transferconduit; and a second thermal fluid circuit adapted to selectablyoperate to circulate the thermal fluid therein, the second thermal fluidcircuit bypassing the first heat exchanger and the passage of the heataccumulator, and comprising the compressor, and a second heat exchanger;operating the system, to circulate the thermal fluid in first thermalfluid circuit, and to circulate the thermal fluid in the second thermalfluid circuit.
 12. The method of defrosting a part of a heat pump systemfor a conditioned space of claim 11, wherein the thermal fluid is arefrigerant.
 13. The method of defrosting a part of a heat pump systemfor a conditioned space of claim 12, wherein the passage of the heataccumulator is at least partially within the heat accumulator.
 14. Themethod of defrosting a part of a heat pump system for a conditionedspace of claim 13, wherein the first thermal fluid circuit and thesecond thermal fluid circuit are conjoined to form a continuous system.15. The method of defrosting a part of a heat pump system for aconditioned space of claim 13, wherein the system is adapted to beoperable to flow the thermal fluid through the first thermal fluidcircuit and to simultaneously flow the thermal fluid through the secondthermal fluid circuit.
 16. The method of defrosting a part of a heatpump system for a conditioned space of claim 14, wherein the system isadapted to be operable to flow the thermal fluid through the firstthermal fluid circuit and to simultaneously flow the thermal fluidthrough the second thermal fluid circuit.
 17. The method of defrosting apart of a heat pump system for a conditioned space of claim 16, whereinthe heat accumulator is adapted to transfer heat from the compressorprimarily by conduction.
 18. The method of defrosting a part of a heatpump system for a conditioned space of claim 16, wherein the heataccumulator is in thermal communication with the compressor through theheat transfer conduit.
 19. The method of defrosting a part of a heatpump system for a conditioned space of claim 18, wherein the heattransfer conduit comprises a solid surface in direct thermal contactwith the compressor.
 20. The heat pump system of claim 1: wherein thethermal fluid is a refrigerant; wherein the heat accumulator a)comprises the solid surface, the solid surface being in direct thermalcontact with the compressor, and is adapted to transfer heat from thecompressor primarily by conduction, or b) is in thermal communicationwith the compressor through the heat transfer conduit, and the heattransfer conduit comprises a solid surface in direct thermal contactwith the compressor; wherein the passage is at least partially withinthe heat accumulator; wherein the first thermal fluid circuit and thesecond thermal fluid circuit are conjoined to form a continuous system;and wherein the system is adapted to be operable to flow the thermalfluid through the first thermal fluid circuit and to simultaneously flowthe thermal fluid through the second thermal fluid circuit.